Sound amplitude limiters

ABSTRACT

This invention pertains to improvements in sound-amplitude limiters, and in particular, incorporates the principle of soundamplitude limiting into a novel device which is self-contained in the ear canal of the user.

United States Patent [191 Glicksberg SOUND AMPLITUDE LIMITERS [76}Inventor: Raymond C. Glicksberg, 704 Santa Mcnica Blvd, Santa Monica,Calif. 90401 [22] Filed: Dec. 26, 1973 [21] Appl. No.: 427,911

Related U.S. Application Data [63] Continuation-impart of Ser. No.253.935, May 17,

1972, abandoned,

[52] US. Cl 179/107 E [51] Int. Cl. 1104p 25/02 [58] Field of Search179/107 R, 107 E [56] References Cited UNITED STATES PATENTS 2.959134511/1960 Ladd 179/107 E [451 June 17, 1975 Wood 179/107 R 9/1970 GeibFOREIGN PATENTS OR APPLICATIONS 598,919 10/1959 Italy 179/107 E PrimaryExaminerRalph Dv Blakeslee [57] ABSTRACT This invention pertains toimprovements in soundamplitude limiters, and in particular, incorporatesthe principle of sound-amplitude limiting into a novel device which isself-contained in the ear canal of the user.

10 Claims, 12 Drawing Figures SOUND AMPLITUDE LlMlTERS The inventionherein described is a continuation-inpart of the now-abandonedapplication filed May 17, I972, Ser. No. 253,935.

Sound-amplitude limiters are devices which limit the intensity of soundreaching the ear drum to a comfort able level while simultaneouslyallowing sounds of lesser intensity to reach the ear drum undiminished,intended for use basically by persons with normal hearing. It is thebasic object of this invention to illustrate how the acousticalprinciple of sound-amplitude limiting can be utilized with ease andpracticality of great numbers of persons who now suffer from thewellpublicized problem of noise pollution. The invention accomplishesthis by adapting the basic acoustical principle of sound amplitudelimiting into a device which is contained within the ear cannal (auralorifice) of the ear, thus rendering the device to be of small size,light in weight, convenient to use, practically or totally unapparent toobservation, and of widespread applicability to the general ambientnoise conditions experienced daily by a vast segment of the population.

SUMMARY OF THE INVENTION A federal governmentsponsored panel hasrecently asserted that noise pollution in the United States was on theverge of reaching a serious level" and has called for new federal andstate standards to protect Americans against hearing damage andannoyance. The panel recommended steps to help eliminate some of the dinof modern living and said the United States should establish a nationalgoal to work toward an environment for all Americans free of noise thatjeopardizes their health and welfare or unnecessarily detracts from thequality of life."

Millions of workers are now exposed to noise levels that have been shownconclusively to produce hearing damage," the panel named by the CommerceDepartment saidv Most of these workers are unaware of the hazard and donot act to protect themselves."

The Department of Health, Education and Welfare should establish interimcriteria and guidelines for use in setting standards to human exposureto noise, the panel said. One of the recommendations of the panel, toestablish an Office of Noise Abatement in the Environmental ProtectionAgency, has been proposed by President Nixon in a bill now before theSenate.

The panel further stated that almost all Americans were responsible forwhat it called a widespread pollutant which can have many adverseeffects on man. The panel said that lSO million Americans living incities and suburbs were exposed to annoying noise that constitutes adegradation of health."

Urban and suburban noise levels are rising with advanced technology andincreased population. exposing the populace to the din of traffic,trucks, sirens, pneumatic drills, machinery, construction and demolitionequipment, horn blasts. squeeling tires, screeching brakes, trains,motorcycles, and riveting guns.

For years now, and in growing numbers daily, residents near jet airportshave been complaining of noise problems, and even attempting legalaction. In another few years, noise problems may be compounded with theadvent of the SST (supersonic transport). This aircraft may not only beas noisy as current aircraft, but may create sonic booms, which, whileof short duration, may be of high intensity. Moreover, the sonic boomgives no warning of its approaching imminence, materializing seeminglyat random to persons on the ground at unpredictable times and withunpredictable intensities. In a few years, then, persons with noprotection from random, high-intensity sound may well suffer in waysdifficult to predict.

Sixty years ago, Robert Koch, Nobel laureate, predicted: A day will comewhen man will have to fight merciless noise as the worst enemy ofhealth. Dr. Vern O. Knudsen, chancellor emeritus of the University ofCalifornia, has said: Noise, like smog, is a slow agent of death. If itcontinues for the next 30 years as it has for the past 30, it couldbecome lethal.

From the above discussion, and an awareness of the general scope andbroad, widespread nature of the problem of noise pollution, it becomesapparent that it has been virtually impossible, within the context ofour present technology, to sufficiently silence our machines,appliances, and all other sources of noise, to an appreciable extent.While it is true that, in some instances, there has been some success inreducing noise levels, the general level of noise continues to increase,due to the incompatability of the operation of present machines with thenon-production of noise. In other words, if the attention ofnoise-abatement endeavors is predominantly focused, as it currently is,upon the present sources of noise, there is relatively little ofpractical value that can be accomplished, as proven by the currentgrowing magnitude of the problem. But. on the other hand, if attentionis transferred from (it source or transmitter of the noise to thereceiver, the ear, then it becomes possible, using non-linear electronicand acoustic techniques, to provide a device which not only subdues andeffectively impedes loud sounds and noises to a level sufficiently lowas to be within the comfort level of the human ear drum, but also,during lapses of the intense noise, permits the user of the device tohear sounds of normal intensity so that they are unsubdued, therebyenabling ordinary conversation, communication, and listening to beunimpaired. [t is for these basic reasons that the device hereindescribed was conceived, offering to the populace a reasonable,workable, and practical solution to many of their noise problems, bymeans of the filtering, dampening, and discriminating of sound energy,allowing only that sound intensity to be heard which is unpainful to thehuman ear.

In addition, it has simultaneously become possible, by utilizing modernmicrominiaturized electronic techniques, to package the device so thatit is situated comfortably, unnoticed, and untroublesome in Nature's ownlittle secret hiding place, the ear canalv Thus, with such tiny,unapparent packaging, and yet retaining a high degree of efficiency, thedevice described herein can be an effective soldier in the battleagainst noise, at last offering the general populace the first practicalmeans for relief against noise pollution.

Other, more specialized applications of this device, and modificationsthereof, mainly for persons who work in high-intermittant-noiseenvironments, but who wish to retain the capacity for conversingnormally with others, such as certain types of industrial workers andsoldiers, for example, may prove to be quite numerous.

Thus, it is a principle object of the present invention to provide adevice which subdues the intensity of ambient sound so that it reachesthe ear drum within the limit of comfort, and simultaneously permitsambient sound which is below the limit of comfort to reach the ear drumundiminishcd.

It is another principle object of the present invention to provide anovel sound-amplitude limiter, in accor dance with the above paragraph,which is worn by the user as a self-contained unit in the outer end ofthe ear canal; and which, for most persons with normal hearing, is wornas an identical pair, one device in each ear canal.

It is another object of the invention to provide a novel sound-amplitudelimiter for limiting the intensity of sound reaching the human ear drumto be below the threshold of discomfort while simultaneously allowingsound below that threshold to reach the ear drum electronicallyreproduced, by means of an earpiece which is worn in the ear canal andwhich contains a sounddeadening substance located between either: (a)the speaker and microphone of a microminiaturized elec tronicsound-reproducing circuit with outputlimiter and power source, or (b)the speaker and soundpowered microphone ofa microminiaturized electronicsound-reproducing circuit with output-limiter.

It is another object of the invention to provide a novel sound-amplitudelimiter as described above which is self-contained in the ear canal andwhich is of the approximate size, shape, and fitness within the earcanal as an ear plug.

It is another object of the invention to provide a novel sound-amplitudelimiter as described above which is self-contained in the ear canal, andwhich is of the approximate size, shape, and fitness within the earcanal as an earplug; such fitness being without soreness or irritationof the ear canal lining membranes by means of an undulating-surfaced,soft, resilient, and flexible earpiece casing which prevents localizedpressure spots from arising between casing and ear canal lining, andwhich said earpiece casings may be manufactured in various shapes andsized, in the case of ready-made" limiters; or such fitness beingprovided by custom-molding said earpiece casing to the shape of the earcanal of the particular user, in the case oftailor-made limiters.

It is another object of the invention to provide a novel sound-amplitudelimiter as described above which is of the approximate size, shape, andfitness within the ear canal as an earplug, which has a soft, flexibleearpiece casing, and which said earpiece is of two attachable andunattachable parts; an inner part towards the inner ear, and an outerpart towards the outer ear.

It is a further object of this invention to provide a novelsound-amplitude limiter as described above, the inner and outer casingsof which are fitted over, contain, and are bonded to, or are moldedover, an inner and outer housing.

It is a further object of this invention to provide a novelsound-amplitude limiter as described above, which said inner and outerhousings typically screw or otherwise attach together, as with a jar andits cover. facilitating an easy change of batteries or repair of theunit, and which said inner and outer housings contain the amplifier withoutput-limiter, the battery or power source, and the microphone, saidmicrophone being positioned at the outermost end of the outer housing,nearest the external ear.

It is a further object of this invention to provide a novelsound-amplitude limiter as described above,

which said amplifier with output-limiter and said microphone areseparated within the inner and outer housings by the battery, suchseparation minimizing any feedback effects.

It is a further object of this invention to provide a novelsound-amplitude limiter as described above, which has a quantity ofsound-deadening material, such as milkweed floss, kapok, glass fibers,or silicone rub ber, positioned as a plug anywhere between themicrophone and speaker of said earpiece, but typically and asillustrated said plug of sound-deadening material being located betweenthe housing and the speaker, said speaker being electrically connectedto the output of the amplifier by two wires which run through saidsound-deadening material.

It is a further object of this invention to provide a novelsound-amplitude limiter as described above whose outer casing is eitherof three basic types: (a) the first type having a broadened outer endwhich blocks any further inward travel of the earpiece within the earcanal, and which said broadened outer end can be used to facilitate theeasy insertion and removal of said earpiece by the fingers of the user;(b) the second type of outer casing not having a broadened end, whichpermits the earpiece to be inserted further within the ear canal so asto be completely unnoticeable from observation, said earpiece in thisinstance having a hook on the outermost end with which a similar butlonger hook can be inserted by the fingers of the user for removal; and(c) the third, or industrial" type of outer casing, especially usefulfor extreme noise conditions, having a spherical outer end protrudingbeyond the ear canal which is filled with additional sound-deadeningmaterial and in which the microphone has been repositioned to theoutermost tip of the outer casing, with the connecting wires of saidmicrophone running through the additional sound-deadening material toterminals in the microphone compartment of the outer housing, which saidmicrophone compartment has also been filled with additionalsound-absorptive material.

It is a further object of this invention to provide a novelsound-amplitude limiter as described above, which said battery of saidsound-amplitude limiter may be removed with the resultant devicebecomingan effective ear plug, especially useful to the user during sleep whichmight otherwise be interrupted by annoying sounds.

In the drawings:

FIG. 1 is an elevational view of the first form of sound-amplitudelimiter, showing the device inserted in the ear canal.

FIG. 2 is an elevational view of the most inconspicuous form ofsound-amplitude limiter, showing the device inserted in the ear canal.

FIG. 3 is a longitudinal sectional view taken along line 3 3 of FIG. 2.

FIG. 4 is an exploded view of the device of FIGS. 2 and 3 inperspective.

FIG. 5 is a graph illustrating the acoustical characteristics ofsound-amplitude limiters, earplugs, and hearing-aids.

FIGS. 6 to 9 illustrate various typical modifications of inner and outercasings.

FIGS. 10 to I2 are perspective views of special and alternative toolswhich can be used for the insertion and removal of the device of FIG. 2.

TECHNICAL DESCRIPTION Referring first to FIGS. 1 and 2, the inventiondescribed herein is typically an earpiece, indicated as a whole by thereference character 15, which utilizes the most modern inmicrominiaturized electronic circuitry and acoustical components,thereby rendering the device not only effective functionally but smallenough to be perhaps completely self-contained within the ear canal 16of the human ear 17, external of the ear drum l8, and practicallyinvisible from human observation, as illustrated in FIG. 2. I

Referring to FIG. 3, in essence the device contains some of thecomponents of modern microminiaturized electronic hearing aids, in thatit contains a miniature PA (public address) system, with microphone l9,battery 20, amplifier-type circuitry with output-limiter 21, and speaker22', and, in addition, contains the soundabsorptive material 23 ofmodern ear-plubs. It is assumed that for most persons, a pair ofsound-amplitude limiters would be worn, one in each ear.

Referring to FIG. 5, sound-amplitude limiters provide their operationalcharacteristics by what might be called discrimination, in that soundinputs above a cer tain maximum-intensity limit, typically taken as thelimit of comfort, are restricted in their output intensity reaching theear drum to an acceptable level for the human car, while those soundinputs below the maximum-intensity limit result in an output intensitywhich is equivalent to the input. This type of operationalcharacteristic is in contrast to hearing aids, which amplify sounds forhard-of-hearing persons up to a maximumintensity limit, but whichprovide no protection against high-intensity sounds; and is also incontrast to ear plugs or ear protectors, which diminish and provideprotection against high-intensity sound, but which simultaneously andproportionally diminish desirable, low and medium-intensity sound suchas conversation, in a linear manner, at each discreet frequency.Soundamplitude limiters, therefore, have unique functionalcharacteristics which render them different from both hearing-aids andear-plugs, and which said unique functional characteristics enablesound-amplitude limiters to be utilized for different purposes, bydifferent persons, and for different situations than either hearing aidsor ear-plugs.

Referring again to FIG. 3, a sound-amplitude limiter is designed so thatmost un-transduced sound, that is, sound which is directly transmittedthrough the material of the device and not converted to electricalsignals and then re-converted back to sound at the speaker 22, isblocked-out from reaching the middle ear by a highly effectivesound-absorbing material 23 which is located within the earpiece 15which is situated in the ear canal, with the exception of acceptable,transduced sound which is converted to electrical signals,output-limited, and transmitted through the sound-absorbing material 23by two wires 24 connecting to the speaker 22 or sound-transducer at theinner tip of the device, nearest the ear drum. Said soundabsorbingmaterial 23 is typically composed of milkweed floss, kapok, glassfibers, or silicone rubber which is capable of attenuating the soundvolume by a factor of approximately 8 times, or 30 decibels, or evenmore. The microphone [9, battery 20, and amplifier-type circuitry (withoutput-limiter and suitable frequencyresponse characteristics) 21 cantypically be located, as

shown, towards the outer end of said sound-absorbing material 23. Thedetailed electronic circuitry actually to be utilized is fully describedin the literature. At the outermost extremity of the device may be atiny hook 25, allowing a person to reach in the ear with a similar butlonger hooking device, such as that shown in FIG. 11, and remove his orher pair of sound-amplitude limiters whenever desired. For the easyinsertion of booktype sound-amplitude limiters into the ear canal, atool such as that shown in FIG. 10 may be used. For both insertion andremoval of hook-type sound-amplitude limiters, a convenient combinationtool such as that shown in FIG. 12 might be used. It is possible thatcertain persons at times may wish to remove the batteries of their pairof sound-amplitude limiters, whereupon the devices become an effectivepair of earplugs useful for sleepers who are bothered by annoyingsounds. Because sound-amplitude limiters can be left in the earscontinuously, with only occasional removal, and because they offer noimpairment to normal hearing, they can provide continuous protectionagainst unpredictable, high-intensity sound energy.

Referring to the longitudinal sectional view of FIG. 3, and the explodedperspective view of FIG. 4, a more complete description of a typicalphysical embodiment of a sound-amplitude limiter can be given.

The earpiece 15 is constructed so as to facilitate the easy change ofbatteries, which is the only maintenance procedure occasionally requiredof the user, besides periodically removing the earpiece from the earcanal for the cleaning of the casing surface. The casing of the earpiece15 is thus composed of two parts, an inner casing 26 nearest the innerear and an outer casing 27 nearest the external ear. Both the inner andouter casings are made of a soft, resilient, and pliable material,typically silicone rubber or latex; and, in the case of ready-madelimiters, having slightly undulating surfaces so that they may readilyconform to the shape of the ear canal upon insertion without creatinglocalized pressure points between casing and ear canal lining membraneswhich can cause soreness and irritation. In addition, such saidundulating surfaces permit an airtight seal between casing and ear canallining, thus enhancing the sound-blocking feature of ready-made devices.

The inner casing 26 and outer casing 27 are fitted over, contain, andare bonded to, or molded over, the inner housing 28 and outer housing29, respectively, which said housings together contain the microphone19, battery 20, and amplifier-type circuitry with output-limiter 21. Thewafer-type battery 20 is situated between the microphone 19 and theamplifier 21 to separate the two and minimize any feedback effects. Theinner housing 28 and outer housing 29 typically screw or otherwiseattach together, as with a jar and its cover, by means of male threads30 on the outermost extremity of inner housing 28, and female threads 31on the innermost extremity of outer housing 29. The inside volumes ofboth the inner housing 28 and outer housing 29 are cylindrical, and whenthe two housings, along with their bonded casings, are unscrewed orotherwise unattached, the battery 20 easily slips out of the cylinder ofthe inner housing 28, whereupon a new battery easily slips in.

The microphone 19, battery 20, and amplifier 21 are positioned withintheir own separate compartments within the housings by means of theouter housing plate 32, and the inner housing plate 33. The outerhousing plate 32 and inner housing plate 33 are each rigidly affixed intheir proper position within the inner cylindrical volumes of the outerhousing 29 and inner housing 28 respectively, but each plate is easilyunfixed and re' moved, if desired, for maintenance or repair of themicrophone 19 or amplifier 21.

The microphone 19 is positioned within the outer end of the outerhousing 29 and covered by the outer housing plate 32. Said microphone 19is positioned with the microphone aperture 56 at the outer end and isheld in place within its compartment by means of rubber spacers 34.

An outer housing plate battery clip 35 clips onto the outer housingplate 32 by means of an arc-shaped notch 36 through said outer housingplate 32. The outer housing plate battery clip 35 lies flat against theouter side of the outer housing plate 32, but protrudes slightly inwardfrom the inner side of said outer housing plate 32, so as to provide aslight spring compression against the battery and tension against themale threads 30 and female threads 31 as the inner housing 28 and outerhousing 29 are screwed together.

The two electrical connections from the microphone l9 and the electricalconnection from the outer housing plate battery clip 35 are made throughthree hairspring-loaded arc-shaped contacts 37 which are evenly spacedabout the outer circular periphery on the inner face of outer housingplate 32. These arc-shaped contacts 37 subtend small arcs which makeconnection with three appropriately mating semi-spherical contacts 38evenly spaced about the outer circular periphery of the outermost faceof the inner housing 28, as the inner housing 28 and the outer housing29 are screwed together and tightened.

The electrical wires connecting from the three semispherical contacts 38to the amplifier 21 run along three grooves 39 on the inner cylindricalwall of inner housing 28.

The amplifier 21 is positioned within the inner end of the inner housing28 and covered by the inner housing plate 33. Said amplifier 21 is heldin place within its compartment by means of epoxy or rubber spacers 40.

An inner housing plate battery clip 41 clips onto the inner housingplate 33 by means of an arc-shaped notch 42 through said inner housingplate 33. The inner hous ing plate battery clip 41 lies flat against theinner side of the inner housing plate 33, but protrudes slightly outwardfrom the outer side of said inner housing plate 33, so as to helpprovide a slight additional spring compression against the battery 20and tension against the male threads 30 and female threads 31 as theinner housing 28 and outer housing 29 are screwed together andtightened.

An electrical wire connects the inner housing plate battery clip 41 tothe amplifier 21 within the amplifier compartment.

The speaker 22 is fitted and bonded within the innermost tip of innercasing 26, so that the acoustic output aperture 42 of speaker 22 isadjacent to the aperture 43 of inner casing 26, which in turn isadjacent to the users ear drum. The flanged edges 44 of inner end plate45 are sandwiched between the tip of inner casing 26 and the tip ofspeaker 22. lnner end plate 45 has tiny apertures 46, the axes of whichare perpendicular to and offset from the acoustic output aperture 42 ofspeaker 22.

Two electrical wires 24 run from two terminals 47 on speaker 22, throughthe sound-deadening material 23 and two holes 48 in the innermost faceof inner housing 28, to the output terminals of amplifier 21.

The soft, resilient inner casing 26, the flexible sounddeadeningmaterial 23, and the pliable, loosely run wires 24 permit approximatelythe innermost half of the device 15 to follow the twist and turn of theear canal, thus insuring proper fitness therein, and preventing anyundue stress on the device itself.

At the outermost end of a "hook-type device 15 is a hook 25 which ispart of outer end plate 49. Outer end plate 49 has tiny apertures 50which are mounted adjacent to aperture 51 of outer casing 27 and tinyapertures 52 of the outermost end of outer housing 29. Outer end plate49 is sandwiched between outer casing 27 and the outermost end of outerhousing 29, said outer end plate 49 being attached to the outermost endof outer housing 29 by means of screws 53 through countersunk holes 54in outer end plate 49 and holes 55 in the outermost end of outer housing29.

FIGS. 6 and 7 illustrate two variations in shape of inner casing 26 asused with hook-type devices.

FIG. 8 illustrates a variation in shape of outer casing 27 as used witha finger-type" device.

FIG. 9 illustrates a typical industrial-type" device which is especiallyuseful for extreme noise conditions. The outer casing 27 has a sphericalouter end protruding beyond the ear canal which is filled withadditional sound-deadening material and in which the microphone 19 hasbeen re-positioned to the outermost tip of the outer casing, with theconducting wires of said microphone 19 running through the additionalsounddeadening material to terminals in the microphone compartment ofthe outer housing, which said microphone compartment has also beenfilled with additional soundabsorptive material. It is possible thatladies would find this type of device especially attractive to wear ifthe outside surface of the sphere were covered with some type ofdecoration.

Various modifications may of course be made from the illustrativeembodiment hereinbefore described and any part may be omitted andreplaced by a substitute which performs the same function or the samefunction plus one or more additional functions, and changes or reversalsof position may be made without departing from the broad spirit of theinvention as succinctly set forth in the appended claims.

The inventor claims:

1. A sound-amplitude limiter which is self-contained in the ear canal ofthe user, and which is used by persons with normal hearing as anindentical pair, comprising:

a. a casing which is adapted to be fitted into the ear canal;

b. a microphone within the outer tip of said casing adjacent theexternal ear;

c. a speaker within the inner tip of said casing adjacent the ear drum,

d. an amplifier-type circuit of nominal gain of one with output-limiterand a battery located within said casing between said microphone andsaid speaker;

. a plug of sound-deadening material located within said casing betweensaid microphone and said speaker, said plug of sound-deadening material9 having two electrical connecting wires passing through it; f. theabove mentioned electronic components hooked-up in operable relationshipas a miniature offset from the acoustic output aperture of said speaker;

b. an outer end plate with a hook is affixed adjacent to the outer endof said outer housing, said outer public address system so that soundinputs above end plate being sandwiched between said outer the limit ofcomfort for the human car are reduced casing and said outer housing andsecured by to that limit at the ear drum. while sound inputs screws Ontoid uter h i d h i aper below said limit are electronically reproduced attures in said outer end plate being aligned with the th ear drum tinyapertures in said outer housing.

The Sound-amplitude limiter of Claim 1 wherein 6. A sound-amplitudelimiter which is self-contained Said cflsing which is adapted to befitted imo in the ear canal of the user, and which is used by per- Canalp of: sons with normal hearing as an identical pair, comprisa. an mnercasing towards the inner ear made of a soft, resilient, pliable materialsuch as rubber or laa. an inner part nearest the inner ear and an outertex, which said inner casing has undulating surfaces 15 part nearest theOuter ear which parts can bg h h hght fhhess Whh'h the ear canal whhoutscrewed or otherwise unattached from each other irri :1 ion.

. when the device is removed from the ear canal for b. an outer casingtowards the outer ear made of the maintenance or batmry change.

f i i mitenal and ,Zh thh Sarhe or b. said inner part containing aspeaker at the inner ar uh u 3 mg 5hr acss as Sal mner Chslhg' ti a luof sound-deadenin material such as 3. The sound-amplitude limiter ofclaim 2 wherein: z gfloss kapok glass fibgfir or suicone a. said innercasing is fitted over, contains, and is and an g cyliridrical g having 3y ai iz I mnetr gi hougmg havmg male lindrical compartment, closed atthe inner end and re'saisproruingoueren; I

b. said outer casing is fitted over, contains, and is f Outer icontdmlhg amplifier 0f bonded to an mner C lindrica] housm havin fenominal gain of one with output-limiter at the inner male breads at itsinger end g g end and having male threads on the protruding outer end;

c. said inner and outer housings, which are contained C Said Outer anmmainin an mner C lindrica by said inner and outer casings,respectively, screw h I d g y together and form a compartment for saidmicrooufmg avmg Cy m Compartment f hone Said batter and said am lifiem 6ch: the inner end and closed at the outer end, contamg y with Output g PW ing a microphone at the outer end and having fel s the i d. saidcompartment is further divided into a microe.thredd nner phonecompartment at the Outer end by an Outer d. said inner cylindricalhousing and said outer cylin housing plate which is rigidly affixed tosaid outer ducal l hh g f Ogether formmg a housing, an amplifiercompartment at the inner end zfi or 3 t by an inner housing plate whichis rigidly affixed to e a men e h Ph Said inner housing and a banewCompartment hooked-up in operable relationship as a miniature tween saidinner and outer housing plates; said miphbhc hddmss System so that soundInputs above crophone and Said amplifier being Separamd by 40 the limitof comfort for the human ear are reduced said battery to minimize anyfeedback effects. that h h the ear drum: whhe Sound inputs 4. Thesound-amplitude limiter of claim 3, wherein: below Sald are electromcahyreproduced at a. said inner and outer housing plates have battery theear drhm- I clips attached thereto which provide a slight com- Thesouhd'amphmde hmher of claim 6 'f 'hpmssion force against the hungrymrminais and a a. said inner part nearest the mner ear is fitted within,slight tension force against said male and female P l i bonded to acylmdlncal-sllapfid threads as said inner and outer housing are screwedmner 635mg hawng an aperture the mner P for together the transmission ofsound from said speaker to the b. the inner face of said outer housingplate contains ear drum 531d mner (135mg 1150 havmg aperture threehairspring-loaded arc-shaped contacts which of sflfficlem and are evenlyspaced about the outer circular periphf g Sald "i Cyllndncal ery, whichsaid arc-shaped contacts subtend small 531d "l 335mg 15 made Ofarelllem: pl arcs and make connection with three appropriatemalenal Suchas rllbbef latex. WhlChSald mn |y mating semi sphericai Comacts gvenlySpaced casing has undulating surfaces enabling tight f tness about theouter circular periphery of the outermost l' Wlthm the ear Canal Withoutface of the inner housing, as the inner and outer q housings are Screwedtogether d i h d; c. said outer part nearest the outer ear is fittedwithin,

cv said arc shaped contacts and said semi-spherical Contained y. nbonded t0 8 Cylindrical-shaped contacts provide electrical connectionfor the two Outer sing ha ing an aperture at the outer tip formicrophone leads and the outer housing plate ba the transmission ofsound from the ambient envitery clip lead to said amplifier. ronment tosaid microphone, said outer casing also 5. The sound-amplitude limiterof claim 4 wherein: having an aperture at the inner end of s fficient a.an inner end plate is affixed adjacent to the inner size to fit over andcontain said outer cylindrical end of said speaker, the flanges of saidinner end housing;

plate being sandwiched between said speaker and said inner casing, andthe axes of the tiny apertures in said inner end plate beingperpendicular to and d. said outer casing is made of a soft. resilient,pliable material such as rubber or latex, which said outer casing hasundulating surfaces enabling tight fitness and conformity within the earcanal without irritation.

8. The sound-amplitude limiter of claim 7 wherein:

a. said inner and outer casings can be made in various shapes and sizesor custom molded for the particular user;

b. said outer part does not have a hook, but said outer casing has abroadened outer tip which limits the inward travel of the device withinthe ear canal and is suitable for finger insertion and removal;

c. said outer part does not have a hook, but said outer casing has anenlarged. spherical outer end protruding beyond the ear canal which isfilled with additional sound'deadening material and in which themicrophone has been re-positioned to the outermost tip of said outercasing, with the connecting wires of said microphone running through theadditional sound-deadening material to terminals in the microphonecompartment of the outer housing. which said microphone compartment hasalso been filled with additional sound-deadening material, rendering thedevice especially useful for extreme noise cinditions.

9. The sound-amplitude limiter of claim 8 wherein:

a. an outer housing plate is rigidly affixed within said outercylindrical housing, which said outer housing plate separates saidmicrophone on the outer side from said battery on the inner side;

b. an inner housing plate is rigidly affixed within said innercylindrical housing, which said inner housing plate separates saidamplifier with output-limiter on the inner side from said battery on theouter side;

c. said microphone and said amplifier with outputlimiter are separatedby said battery to minimize any feedback effects;

d, said inner and outer housing plates have battery clips attachedthereto which provide a slight compression force against the batteryterminals and a slight tension force against said male and femalethreads as said inner and outer cylindrical housing are screwed togetherand tightened;

e. the inner face of said outer housing plate contains threehairspring-loaded contacts which are evenly spaced about the outercircular periphery, which said contacts subtend small arcs and makeconnection with three appropriately mating semi-spherical contactsevenly spaced about the outer circular pe riphery of the outermost faceof the inner housing, as the inner and outer housings are screwed together and tightened;

f. said contacts provide electrical connection for the two microphoneleads and the outer housing plate battery clip lead to said amplifier;

g an inner end plate is affixed adjacent to the inner end of saidspeaker, the flanges of said inner end plate being sandwiched betweensaid speaker and said inner casing, and the axes of the tiny aperturesin said inner end plate being perpendicular to and offset from theacoustic output aperture of said speaker;

h an outer end plate with a hook is affixed adjacent to the outer end ofsaid outer housing, said outer end plate being sandwiched between saidouter casing and said outer housing and secured by screws onto saidouter housing, and the tiny apertures in said outer end plate beingaligned with the tiny apertures in said outer housing.

10. A sound-amplitude limiting device which is selfcontained in the earcanal of the user, which is used by persons with normal hearing as anidentical pair, and which is of the approximate size, shape, and fitnesswithin said ear canal as an ear-plug; which said device limits theintensity of environmental sound reaching the ear drum to be below thelimit of comfort while simultaneously allowing environmental sound belowsaid limit of comfort to reach the ear drum undiminished, by means of ahighly-effective sound-deadening substance located between the speakerand microphone of a microminiaturized electronic sound-reproducingsystem including battery and amplifier-type circuitry of nominal gain ofone with outputlimiter, said speaker being located at the inner tip ofthe device nearest the ear drum. and said microphone being located atthe outer tip of the device nearest the external ear,

l k l

1. A sound-amplitude limiter which is self-contained in the ear canal ofthe user, and which is used by persons with normal hearing as anindentical pair, comprising: a. a casing which is adapted to be fittedinto the ear canal; b. a microphone within the outer tip of said casingadjacent the external ear; c. a speaker within the inner tip of saidcasing adjacent the ear drum; d. an amplifier-type circuit of nominalgain of one with outputlimiter and a battery located within said casingbetween said microphone and said speaker; e. a plug of sound-deadeningmaterial located within said casing between said microphone and saidspeaker, said plug of sounddeadening material having two electricalconnecting wires passing through it; f. the above mentioned electroniccomponents hooked-up in operAble relationship as a miniature publicaddress system so that sound inputs above the limit of comfort for thehuman ear are reduced to that limit at the ear drum, while sound inputsbelow said limit are electronically reproduced at the ear drum.
 2. Thesound-amplitude limiter of claim 1 wherein said casing which is adaptedto be fitted into the ear canal is comprised of: a. an inner casingtowards the inner ear made of a soft, resilient, pliable material suchas rubber or latex, which said inner casing has undulating surfacesenabling tight fitness within the ear canal without irritation. b. anouter casing towards the outer ear made of the same of similar materialand with the same or similar undulating surfaces as said inner casing.3. The sound-amplitude limiter of claim 2 wherein: a. said inner casingis fitted over, contains, and is bonded to an inner cylindrical housinghaving male threads at its protruding outer end; b. said outer casing isfitted over, contains, and is bonded to an outer cylindrical housinghaving female threads at its inner end; c. said inner and outerhousings, which are contained by said inner and outer casings,respectively, screw together and form a compartment for said microphone,said battery, and said amplifier-type circuitry with output-limiter; d.said compartment is further divided into a microphone compartment at theouter end by an outer housing plate which is rigidly affixed to saidouter housing, an amplifier compartment at the inner end by an innerhousing plate which is rigidly affixed to said inner housing, and abattery compartment between said inner and outer housing plates; saidmicrophone and said amplifier being separated by said battery tominimize any feedback effects.
 4. The sound-amplitude limiter of claim3, wherein: a. said inner and outer housing plates have battery clipsattached thereto which provide a slight compression force against thebattery terminals and a slight tension force against said male andfemale threads as said inner and outer housing are screwed together; b.the inner face of said outer housing plate contains threehairspring-loaded arc-shaped contacts which are evenly spaced about theouter circular periphery, which said arc-shaped contacts subtend smallarcs and make connection with three appropriately-mating semi-sphericalcontacts evenly spaced about the outer circular periphery of theoutermost face of the inner housing, as the inner and outer housings arescrewed together and tightened; c. said arc-shaped contacts and saidsemi-spherical contacts provide electrical connection for the twomicrophone leads and the outer housing plate battery clip lead to saidamplifier.
 5. The sound-amplitude limiter of claim 4 wherein: a. aninner end plate is affixed adjacent to the inner end of said speaker,the flanges of said inner end plate being sandwiched between saidspeaker and said inner casing, and the axes of the tiny apertures insaid inner end plate being perpendicular to and offset from the acousticoutput aperture of said speaker; b. an outer end plate with a hook isaffixed adjacent to the outer end of said outer housing, said outer endplate being sandwiched between said outer casing and said outer housingand secured by screws onto said outer housing, and the tiny apertures insaid outer end plate being aligned with the tiny apertures in said outerhousing.
 6. A sound-amplitude limiter which is self-contained in the earcanal of the user, and which is used by persons with normal hearing asan identical pair, comprising: a. an inner part nearest the inner earand an outer part nearest the outer ear which parts can be unscrewed orotherwise unattached from each other when the device is removed from theear canal for maintenance or battery change; b. said inner partcontaining a speaker at the inner tip; a plug of sound-deadeningmaterial such as milkweed floss, kapok, glass fiber, or silicone rubber;and an inner cyliNdrical housing having a cylindrical compartment,closed at the inner end and open at the outer end, containing anamplifier of nominal gain of one with output-limiter at the inner endand having male threads on the protruding outer end; c. said outer partcontaining an outer cylindrical housing having a cylindricalcompartment, open at the inner end and closed at the outer end,containing a microphone at the outer end and having female threads onthe inner end; d. said inner cylindrical housing and said outercylindrical housing when screwed together forming a compartment for saidbattery; e. the above mentioned electronic components hooked-up inoperable relationship as a miniature public address system so that soundinputs above the limit of comfort for the human ear are reduced to thatlimit at the ear drum, while sound inputs below said limit areelectronically reproduced at the ear drum.
 7. The sound-amplitudelimiter of claim 6 wherein: a. said inner part nearest the inner ear isfitted within, contained by, and bonded to a cylindrical-shaped innercasing having an aperture at the inner tip for the transmission of soundfrom said speaker to the ear drum, said inner casing also having anaperture at the outer end of sufficient size to fit over and containsaid inner cylindrical housing; b. said inner casing is made of a soft,resilient, pliable material such as rubber or latex, which said innercasing has undulating surfaces enabling tight fitness and conformitywithin the ear canal without irritation; c. said outer part nearest theouter ear is fitted within, contained by, and bonded to acylindrical-shaped outer casing having an aperture at the outer tip forthe transmission of sound from the ambient environment to saidmicrophone, said outer casing also having an aperture at the inner endof sufficient size to fit over and contain said outer cylindricalhousing; d. said outer casing is made of a soft, resilient, pliablematerial such as rubber or latex, which said outer casing has undulatingsurfaces enabling tight fitness and conformity within the ear canalwithout irritation.
 8. The sound-amplitude limiter of claim 7 wherein:a. said inner and outer casings can be made in various shapes and sizesor custom-molded for the particular user; b. said outer part does nothave a hook, but said outer casing has a broadened outer tip whichlimits the inward travel of the device within the ear canal and issuitable for finger insertion and removal; c. said outer part does nothave a hook, but said outer casing has an enlarged, spherical outer endprotruding beyond the ear canal which is filled with additionalsound-deadening material and in which the microphone has beenre-positioned to the outermost tip of said outer casing, with theconnecting wires of said microphone running through the additionalsound-deadening material to terminals in the microphone compartment ofthe outer housing, which said microphone compartment has also beenfilled with additional sound-deadening material, rendering the deviceespecially useful for extreme noise cinditions.
 9. The sound-amplitudelimiter of claim 8 wherein: a. an outer housing plate is rigidly affixedwithin said outer cylindrical housing, which said outer housing plateseparates said microphone on the outer side from said battery on theinner side; b. an inner housing plate is rigidly affixed within saidinner cylindrical housing, which said inner housing plate separates saidamplifier with output-limiter on the inner side from said battery on theouter side; c. said microphone and said amplifier with output-limiterare separated by said battery to minimize any feedback effects; d. saidinner and outer housing plates have battery clips attached thereto whichprovide a slight compression force against the battery terminals and aslight tension force against said male and female threads as said innerand outer cylindrical housing are screwed together and tightEned; e. theinner face of said outer housing plate contains three hairspring-loadedcontacts which are evenly spaced about the outer circular periphery,which said contacts subtend small arcs and make connection with threeappropriately mating semi-spherical contacts evenly spaced about theouter circular periphery of the outermost face of the inner housing, asthe inner and outer housings are screwed together and tightened; f. saidcontacts provide electrical connection for the two microphone leads andthe outer housing plate battery clip lead to said amplifier; g. an innerend plate is affixed adjacent to the inner end of said speaker, theflanges of said inner end plate being sandwiched between said speakerand said inner casing, and the axes of the tiny apertures in said innerend plate being perpendicular to and offset from the acoustic outputaperture of said speaker; h. an outer end plate with a hook is affixedadjacent to the outer end of said outer housing, said outer end platebeing sandwiched between said outer casing and said outer housing andsecured by screws onto said outer housing, and the tiny apertures insaid outer end plate being aligned with the tiny apertures in said outerhousing.
 10. A sound-amplitude limiting device which is self-containedin the ear canal of the user, which is used by persons with normalhearing as an identical pair, and which is of the approximate size,shape, and fitness within said ear canal as an ear-plug; which saiddevice limits the intensity of environmental sound reaching the ear drumto be below the limit of comfort while simultaneously allowingenvironmental sound below said limit of comfort to reach the ear drumundiminished, by means of a highly-effective sound-deadening substancelocated between the speaker and microphone of a microminiaturizedelectronic sound-reproducing system including battery and amplifier-typecircuitry of nominal gain of one with output-limiter, said speaker beinglocated at the inner tip of the device nearest the ear drum, and saidmicrophone being located at the outer tip of the device nearest theexternal ear.